Electric lifting device



D 8, 1 42- F. w. HORSTKOTTE 2,304,360

ELECTRIC LIFTING DEVICE I Filed Dec. 24, 1940 2 Sheets-Sheet 1- Z3 /2[we 3790752 INVENTOR FknER/ak WHo RSTKO 77's Dmyafl ATTORNEY Dec. 8,1942. F. w. HORSTKOTTE ELECTRIC LIFTING DEVICE Filed Dec. 24, 1940 2Sheets-Sheet 2 LINEETARTEE INVENTOR Fkg'DE/P/cyq W Ho/vs r/ro F'TEATTORNEY Patented Dec. 8, 1942 the art is referred this specification. Iv .v

, 'Ifqilltistrate mechanism adapted to"apply the" of great intensity, asfor." enampl It 15am bi ct t'tntr sntim i steam cylinder fare manycited, but they have been] concomitants of .apparatu ing therequiredfunction, a I) Such apparatus is ordinarily :u'sed nterinittently andfor only a, verysnialldrahtion of total working time, hence it is anobject to as- "sociate a suitable electric motor with suitable" ,otherelements in such a comhinationthat wheri""-- a starting impulse ismanually'-given, 'the motor has initial room in its operating cyn attainspeed and power without having tofac'cfept substantial loaduntil itfhasdone this; yet it must and does enter the work part'of the cycle withoutshock uch as "may be expected with employment ,of aclutchg'jwhich inthis'finvention is not used.

" It istherefore another obiectiof the present in-*" v vention toprovide electrically operated apparatus" ,having operatingchamacigeristics as indicated,

, but omittinga clutch heretofore always deemed necessary.

' j succinctly; t is anfobject of thisinventionto' arrange an electricalsubstitute for the steam cylinder and piston device, that fulfills all0: 3

' shaft and 3 is a shunt brake, see Fig. VIII, and

the functio'ns of the-latter atits 'best anddoes not have its inherent--infirmities, such as a tendency toovershootdue to resilient steam whenTo-comply with Sec. 4888 mg arm forthrowing a log onto asaw carriage.

- This -however, is only one of;;the very numerous 1 applications.wherein it :is an advance-over the 3 reciprocating steam '2 cylinderand; piston;'henceathe'drawings will not' -be regarded asilimiting butillustrative only. For the scope of the invention,-,v;; 2-

to-the claimsat the closer'of' me(:l'ianical principles of thisinvention; drawings a. s.';' i have sh 'y 7 my new invention operatiyelyconnected to a load-' electric' power as instantly availablelas' steamcylinder, withjpiston hereto for, such. requirements.

accompany and area-made 1'0WS v a 'Fig; I is a side elevation oft-anoperative log lifting device forthrowing a logonto a saw-car- 1 riagethat embodies the principlenfthe present invention andthis flgurealsoincludes a diagram- -='matic layout :of the electricalconnectionsmore -c'ompletelyi shown in detailv in Fig .}VI II;

Fig. II is a- -left hand end" view of the structure sh'own'in Fig-'VI Q-1 Figrnr is a anaemia Fig. I; IV-is a. section taken at=IV-IV,,Fig. I,

- thelast two figureswbeing especially useful to show Fig.. V';.,'1'Fig. VII is a, "useful in cases-,whereavery long stroke is re- 1 thepositioneof limit switches and their employ- 'ment i-as hereinafter;described};

Fig-V is a-diagram showing ho wa pair of limit switches vmay be usedwitha single operative cam,

f' the structure being otherwise thesamein princit pleas that shown inFig. I; I e

'Fig.- VI isa view in orthograp pro)ection of view of'an alternateconstruction,

-quired' or "where more than two or three limit switchesare desirablein- 1eac h cycleof operation;

FigavIlI-isawiringdiagram for the structure shown in Fig. I, fromwhich'any skilled electrician the-load changes, or reversely to drop a'load due to steam conde'nsation, .often .occurring with ex-" 1tremerapidity.. The very substantial waste of v "power"; of a steamlifter using. steam non-ex pansively is also avoided.

may make up a wire diagram for any-variation thereof employing the sameprinciple.

In the drawings, flrst-,consideri ng Fig. I:. l is an electric motor: ofthe 3 phase squirrel cage 1 type with an 'exceedinglyhigh' startingtorque, "8,150 capable of carrying a momentary overload of severalhundred percent, 2 is the motor drive is the single phase circuit-forthe brake. This type of brake is set;by a spring and opened by gears-runin oil, delivering the motor power to an output shaft 6; at relativelyslow speedand correspondingly increased torque. This motorgear will haveto be strong enough tooperate satisfactorily when the motor isdelivering its maximum overload capacity..

A crank-'I-is-mount d on the shaft 5. It has a crankpin. Bto- .wh-ich.oneend of. theconnecting rod 9 is journalledn The --;other ,end'of theconnecting rod! is journalled between theforks ID of the rockerv arm ll,which is made rigid with the rockshaftll. A wrist pin ll-' holdstheconnecting rod 9-operatively between the forks.

The rock shaft 12 is adapted to oscillate under influence of the motor Iby means of the transmissions heretofcre described and, when sooscillated, will apply great power to the lifter arm I3, a well knowndevice for throwing a log from a log-deck to a saw carriage, asindicated in Fig. -11, though always heretofore such a lifter has beenoperated by a double acting steam cylinder of considerable size. Inpractice there will be at least two of these lifter arms.

It will be at once apparent that any other severe but short time lift,other than the one shown, may be accomplished by appropriate drivenelectrically operated devices according to this invention. Note herethat a crank or similar transmission has a neutral zone of operationwhile it is going over its bottom center. Being halted at the bottomcenter of its stroke or just before it reaches the bottom, and assumingthat the reduction in the motorgear is considerable, a motor with a highpullout torque will attain a high speed and consequent pulling powerbefore it must accept any substantial part of the load, represented hereby a log L, in dotted outline, then the great momentary overloadcapacity of the motor will be put to good use, be-

cause the lift will be completed well short of the time when the copperwindings of the motor can overheat due to abnormal current flow.

It is believed that this marks the first time this inherent motorcharacteristic has been put to beneficial use, save to occasionallyprevent damage when some operated part is stuck.

That this structure may be operated with a facility superior to thesteam cylinder lifter which it replaces, may now be examined into.

We will assume that the electric lifter is at rest, as shown at Fig. I,with the crank-pin 8 somewhere within the neutral zone of itsrevolution, as shown. The limit switch has been opened by the cam 2| onthe hub of the crank 1; hence the primary line 22 of the electric motorcircuit is dead. The head-sawyer will step on the manually operable,normally open switch 23, thus closing the secondary electric line 24 and25, whereupon the limit switch 20 is by-passed, the manual switch 23takes over control, the shunt brake 3 instantly releases and the motoroperates the electric lift after the manner described.

If actuation of the manual switch is momentary only, being released assoon as the lift starts, then the limit switch 20 takes over thecontrol, until the cam 2| lifts the arm 30, of the limit switch 3|,whereupon the secondary line is again opened with the lifting arm II ontop in the position shown in Fig. II and the motor stops abruptly.

The brake will stop the motor i without overrun suiiicient to interferewith successful operation, when a log turner or a device for shoving thelog further onto the carriage may be worked,

the lifter l3 meanwhile holding the log L exactly where it was placedfor any desired length of time, something for whichthe steam cylinder isnot well suited.

If, on the other hand, -mere throwing of the log onto the carriage issumcient', then the operator will keep the manual switch closed untilthe arm l3 begins the downward part of its cyclic operation, when hereleases it and the limit switch 20 assumes control automatically. Thiscycle of operations is more certain than that of a steam cylinder anddoes not involve the very large waste of power occasioned by a directsteam pressure in a cylinder.

In Figs, V and VI. there is shown a disc ll, upon which is mounted asingle cam ll, cooperative with limit switches .42 and 43. The mode ofoperation of this form is identicalwith that shown in Fig. I, but byplacement of the limit switches differently, a single cam serves just aswell as two cams in the other structure. It will be apparent that camoperated limit switches can be placed adjacent any part having a cyclicpath of operation.

Fig. VII illustrates a chain 50 mounted on a driving sprocket 5| and adriven sprocket 52, to which is pinned a connecting rod 53. A singlelimit switch 54 will be opened by a cam 55, shown as an attachment linkof the chain 60. Obviously this structure lends itself well to carryingseveral more cams than are conveniently disposable within the workingcycle of the transmissions of Fig. I- The purpose of this figure is toshow that by proper modification of the structure shown in Fig. I anoperating cycle of a lifter can be varied even more widely than with thewell known steam cylinder lift and with the added advantage thatwherever it is stopped, ii will stay, indefinitely until it is purposelymoved forward. In practice, there are at least two and generally threepositions on the lifting side of the operating cycle, with nothing onthe return side save a limit switch positioned to stop the crank-pin orequivalent structure within the neutral zone and preferably Just at itsbeginning, lucidly expressed by using a marksmans simile, atfive-o-clock."

Having disclosed my invention and explained its principle so that it cantake its proper place in the art, what I claim as new and desire tosecure by Letters Patent is:

1. Anflelectric log lifting and moving device comprising a lifter arm, acrank connected to said arm, an electric motor operatively connected tosaid crank, control means for said motor comprising a power circuit, twoautomatic limit switches in said circuit, means for operating said limitswitches seriatim to stop the motor with the crank in its nextsucceeding neutral zone, and a normally open manual switch effective tobypass both automatic limit switches for continuous operation of themotor when it is forcibly held in closed Position.

2. An electrically operated lifter device comprising a reciprocatinglifter crank, means for reciprocating the lifter comprising an electricmotor, speed reducing transmission means connected intermediate themotor and the crank, a pair of cams revoluble at crank speed andsynchronized therewith, anelectric. circuit for said motor, a pair ofautomatic limit switches in said circuit, an operating cam for eachswitch. a bypass circuit, and a normally open manual switch in saidcircuit effective upon operation to take over control from both of theautomatic limit switches, each limit switch and cam for operating thesame being timed to stop the crank in its next succeeding neutral zone.

3. An electric lift comprising an electric motor. a power circuit forsaid motorycontrol means comprising a normally open manual switch andtwo automatic limit switches, a reciprocable lifter, transmissionsbetween the lifter and the motor, a crank forming part of saidtransmissions, and limit switch operating means synchronous with thecrank and timed to operate one of the limit switches and stop the motorwith the crank in its nearest neutral zone, the said manual switcheffective to assume and hold control of the motor when manually closed.

4. In an electric lifter, an electric motor therefor, transmissions forsaid motor effective to change rotary to reciprocating motion at reducedspeed, crank and connecting rod means in series with other parts in saidtransmissions, a pair of revoluble cams synchronized with the crank, apair of, normally closed limit switches arranged to be opened seriatimby the cams to stop the motor and leave the crank in a neutral zone, anda normally open manually operable switch arranged to supersede thecontrol of any given limit switch that may have stopped the motor, to

restart the same, each limit switch being eflective, seriatim, to stopthe crank as it enters its next neutral zone.

5. An electric lilting device comprising an electric motor, a crankdriven thereby, speed reducing transmissions therebetween, a litteroperable by the crank, said trons comprising one part having a cyclicpath of movement. cams made rigid with said last named part, a pair ofnormally closed'limit switches arranged to be opened seriatim by saidcams, each of said limit switches eilective to stop the motor leavingthe crank in its nearest neutral zone when contacted by a cam, and anormally open manual switch effective to by-pass both limit switcheswhen closed.

mnnmrcx w. nonsrxo rra.

